A piezoelectric body produces a distortion when an electrical input is applied. This is referred to as the inverse piezoelectric effect. Features of this piezoelectric body include high output, high response, and non-magnetism. A high-output actuator can be fabricated using a piezoelectric body.
In the past, components of piezoelectric actuators have been machined and assembled one by one by etching or using an NC (numerical control) machine or the like. A specific known example of such a piezoelectric actuator is a piezoelectric micromotor (The Institute of Electrical Engineers of Japan, 15th Sensor Symposium, TECHNICAL DIGEST, pp. 181-184, 1997). FIG. 2 is an assembly view of this piezoelectric micromotor. This piezoelectric micromotor comprises a disc-like moving body 4 having a salient axial portion and a base chassis 17 holding a vibrating body 3 and the salient shaft portion. The vibrating body 3 has three bending-and-displacement mechanisms 18, each being constructed of a piezoelectric body 1 producing expanding and contracting motions, the piezoelectric body 1 being stuck to a vibrator 2. Each bending-and-displacement mechanism 18 assumes an L-shaped form. The end of the shorter side of this L-shaped mechanism is fixedly mounted to the center portion of the base chassis 17. The bending-and-displacement mechanisms 18 are placed parallel to the tangential direction of the moving body 4. This moving body 4 has a sliding portion. The vibrator 2 is fabricated by etching or other process. FIG. 3 illustrates the principle of operation of this piezoelectric micromotor. When an exciting voltage of a certain frequency is applied to the piezoelectric body 1, this piezoelectric body 1 expands and contracts. This bends and vibrates the vibrator 2 as shown in FIG. 3. As the vibrator 2 vibrates, the front end of the vibrator 2 makes contact with the moving body 4. As a result of the combination of the vertical and lateral force components, the moving body 4 is moved.
Since the conventional piezoelectric actuators have been assembled one by one, the productivity is associated with problems. Additionally, fabrication costs have been high. Microdevices fabricated by combining microparts are quite small and so it is necessary that a large number of microdevices be incorporated into one finished product. Therefore, there is a need for a technique for manufacturing a large number of microdevices at a time by batch processing rather than fabricating small-sized products one by one.
Therefore, a great number of parts have been fabricated in a short time by etching or other techniques. Where etching or other similar technique is used, it is possible to mass-produce microparts on one plate. However, it is necessary to establish procedures for separating them into desired shapes and for efficiently assembling the microparts.
FIG. 13 is a top plan view showing one example of cutting of the connector portion of the vibrating body 3. The vibrating body 3 is completely mounted fixedly at a stationary portion 12. Where a connector portion 8 is cut by dicing technology, for example, it is severed along a cut portion 10. Unfortunately, a protruding portion such as a burr 11 is produced. Even if an accurate machining operation is carried out, a minute burr 11 will be formed.
Dicing technology, laser processing, etching, and other technologies have been available as methods of separating individual components as described above. With any technique, there arises the problem that formation of burrs or dimples results. Therefore, a burr left on the vibrator may drag along the moving body, or the burr may add to the mass, thus affecting the amplitude of the vibration. This may deteriorate the driving performance.
Where a method of forcedly plastically deforming or cutting the material such as a punch is used, force is applied to the vibrator. This may deform the vibrator.
Especially, a piezoelectric actuator makes use of a resonance phenomenon. The resonance frequency may be varied according to the accuracy of the vibrator parts. Consequently, in order to offer uniform driving performance, the machining operation must be performed and the actuator must be designed such that improved accuracy is obtained or the resonance phenomenon is affected less.